Exploration of angular's ngClass directive

Question

Exploration of angular's ngClass directive

I've been diving into the world of AngularJs and recently created a simple Angular application. In one section of this app, I utilized ngClass within a div element like below:

<div ng-class='{"some class": aFuncTruthyOrFalsy()}'>
<!-- The aFuncTruthyOrFalsy() function is implemented in the controller specific to this view-->

Interestingly, there's an unrelated input field in the same view that has no association with the aforementioned div or the values checked within the function.

I observed that every time I type something in the input field (be it a change event or keypress event), it triggers a reevaluation of the ngClass. (I confirmed this by adding a console log inside the aFuncTruthyOrFalsy function). I'm puzzled as to which events are actually causing this frequent reevaluation.

It appears that ngClass undergoes reevaluation upon each and every event occurrence on the page.

Could someone shed some light on this behavior?

Is there a way to cache the evaluated class during the initial loading of the view?

Moreover, imagine if multiple ngClass directives are used within the same view, and each expression evaluation is handed over to functions that perform complex operations to arrive at the final evaluated expression? How would that impact performance and behavior?

javascript angularjs ng-class

Answer 1

Answer №1

In Angular, binding involves using $watch to track changes in function values. The digest cycle triggers your function to compare its result with the previous one.

For further explanation, check out this helpful article:

I recommend binding to scope variables instead of functions. Create a variable in the scope to store the function's result and update it as needed. This way, you avoid calling methods directly from the view, which could potentially compromise the MVC architecture if unexpected functionality is added to those methods.

Answer 2

In Angular, binding involves using $watch to track changes in function values. The digest cycle triggers your function to compare its result with the previous one.

For further explanation, check out this helpful article:

I recommend binding to scope variables instead of functions. Create a variable in the scope to store the function's result and update it as needed. This way, you avoid calling methods directly from the view, which could potentially compromise the MVC architecture if unexpected functionality is added to those methods.

Answer 3

Answer №2

Changing something in the scope of AngularJS will automatically initiate a $digest cycle with a call to $digest(). During this $digest cycle, each watcher is executed.

Angular places a watcher on the scope model, ensuring that the view is updated whenever there are changes to the model.

Therefore, when alterations are made to the scope, all watchers are triggered and the model is reassessed.

If you want to learn more about this topic, check out this informative article: Link

Answer 4

Changing something in the scope of AngularJS will automatically initiate a $digest cycle with a call to $digest(). During this $digest cycle, each watcher is executed.

Angular places a watcher on the scope model, ensuring that the view is updated whenever there are changes to the model.

Therefore, when alterations are made to the scope, all watchers are triggered and the model is reassessed.

If you want to learn more about this topic, check out this informative article: Link

Answer 5

Answer №3

Here is an example of how you can achieve this:

 <div ng-class="{'background1': color.back}">
    <label> <span>{{emp.comp}}</span> </label>
  </div>

Answer 6

Here is an example of how you can achieve this:

 <div ng-class="{'background1': color.back}">
    <label> <span>{{emp.comp}}</span> </label>
  </div>

Exploration of angular's ngClass directive

Answer №1

Answer №2

Answer №3

Similar questions

Tips for implementing async/await with the file system module

Enhance the functionality of a directive by incorporating the ui-mask directive

When it comes to AFrame+Three.js, which is more efficient: having numerous meshes with minimal triangles per mesh or having a few meshes with a high number of

Discovering an item using two different text inputs

What type does a React stateless functional component Flow return?

Conceal Navigation with jQuery

Retrieving property values from an object across multiple levels based on property name

Attempting to include an additional choice in a dropdown menu

Navigating through JavaScript list items

What is the best way to serve index.html from a Node.js/Express application?

Jade: Error Alert! Unexpected Identifier Detected on Ubuntu, whereas Mac Compatibility Confirmed

Is it possible to enhance the appearance of the select2 options in any way?

What could be causing this slider to malfunction in Firefox?

What is the syntax for accessing an element within an array in a function?

Unable to use the .focus() method on a Link component by utilizing references in React Router 4

Resolving the "Error: Cannot update a React state on an unmounted component" issue

Struggling with eliminating the # from a URL in AngularJS

Form validation on the client side is not occurring, and the form elements cannot be edited

What is the best way to update HTML element contents with new code without losing any associated JavaScript functions?

Is it advisable to include both Node.js API and Angular.js in a single project?